1. Field of the Invention
This invention relates to a vaccine effective against infections with Gram-negative bacteria and lipopolysaccharide (“LPS”)-mediated pathology induced by Gram-negative bacterial infections. More particularly, it relates to a non-covalent, polyvalent complex vaccine containing purified E. coli LPS endotoxin and purified N. meningitidis outer membrane protein, which vaccine produces, in an actively immunized subject, an immune response against Gram-negative bacterial infection and the pathology caused by the LPS endotoxin. The present invention also relates to production of specific polyclonal antibodies that can be used to protect a second subject passively against Gram-negative bacterial infections and LPS-mediated pathology.
2. Description of the Background Art
Infections by Gram-negative bacteria and consequent septic shock are leading causes of death among hospitalized patients. It is estimated that Gram-negative sepsis has an incidence of 70,000 to 300,000 cases per year in the United States. McCabe et al., Am. J. of Med. 68: 344 (1980).
It is well-documented that a principal mediator of Gram-negative bacterial septic shock is a LPS endotoxin present on the outer membrane of Gram-negative bacteria. Luderitz et al., Rev. Infect. Dis. 61: 428 (1984); Rietsckel et al., loc. cit. 9(suppl.): 5527 (1987).
Attempts have been made to produce vaccines that will produce anti-endotoxin antibodies, and thereby protect against septic shock. For a review, see Cross et al., J. Endotox. Res. 3: 57 (1994). Ziegler et al., N. Eng. J. Med. 107: 1225 (1982) showed in a clinical setting that polyclonal antiserum obtained from volunteers immunized with boiled E. coli J5 (Rc chemotype) provided significant protection. In another study, however, the human polyclonal antibody to J5 boiled cell vaccine was not superior to normal human IgG in reducing death from Gram-negative bacteremia. Calandra et al., J. Infect. Dis., 158:312 (1988). On the other hand, more recently it was shown that affinity-purified IgG derived from the serum of rabbits immunized with J5 boiled cell vaccine afforded neutropenic rats substantial protection against challenge with Ps. aeruginosa, a heterologous Gram-negative bacteria. Bhattacharjee et al., Clin. Res. 41(2): Abs 247 (1993). These contradictory reports point up the uncertainty and unpredictability of using boiled J5 LPS as a vaccine.
Disappointing results also have been reported in the use of anti-endotoxin monoclonal antibodies. Clinical trials of the HA-1A human monoclonal antibody (Ziegler et al., N. Eng. J. Med. 324: 429 (1991)), and the ES murine monoclonal IgM antibody (Greenman et al., J. Am. Med. Assoc. 266: 1097 (1991); Wenzel et al., 31st Intl. Conf. Antimicrob. Agts. Chemotherapy 240, Abstr. 1170 (1991)) did not generate data adequate to support product licensing. Cross et al. (1994), above.
Earlier, Kanegasaki et al. in BACTERIAL ENDOTOXIN: CHEMICAL, BIOLOGICAL AND CLINICAL ASPECTS, Homma et al., eds. (Verlag Chemie, 1984), complexed various crude LPS preparations with an outer membrane protein derived from E. coli and compared these complexes in two systems, namely, induction of interferon production in rabbit spleen cells and activation of preclotting enzymes of the horseshoe crab. It was reported that differing degrees of activity were exhibited by complexes derived from different LPS preparations, and that substituents not masked after complex formation are in part responsible for the variability of activity. This, in turn, may be a reflection of the great variability of the O-polysaccharide chain structure of LPS's even among different strains of the same species. For example, there are over 100 serotypes of E. coli based on the structure of O-polysaccharide. Kenne et al. in 2 POLYSACCHARIDES 282, G.O. Asoinall, eds. (1983).
Because of these uncertainties and an unmet need of long-standing for a vaccine effective against Gram-negative bacterial infections, the present inventors have devised a novel vaccine which allows for both active and passive immunization against Gram-negative bacterial infections.